Miniature potentiometer with stop rib and sealing means

ABSTRACT

A miniature potentiometer including a housing having an integral internal rib forming a stop; a bottom plate assembly incorporating a resistance element and terminal contacts and having a groove receiving the rib and locking the bottom plate against rotation in the housing; and a rotatable carrier assembly carrying a contact spring engageable with the resistance element and having a projection engageable with the rib for limiting rotation of the carrier assembly.

stateS Patent 1 Scheiterbauer et al.

MINIATURE POTENTIOMETER WITH STOP RIB AND SEALING MEANS Inventors: Adolf R. Scheiterbauer, Munich;

Helmut Stickdorn, Neubiberg, both of Germany Assignee: The Bunker-Ramo Corporation, Oak

Brook, 111.

Filed: Dec. 2, 1971 Appl. No.: 204,381

Related U.S. Application Data Continuation of Ser. No. 36,077, May 11, 1970,

abandoned.

US. Cl. 338/164, 338/174 Int. Cl 1101c /02, H016 9/02 Field of Search 338/162-164,

References Cited UNITED STATES PATENTS 2/1966 Barden 338/164 [4 1 July 31, 1973 Scheel 338/162 3,355,693 11/1967 Van Benthuysem. 338/202 X 3,377,606 4/1968 Ferrell 338/164 X 3,380,011 4/1968 Basket 338/162 3,537,056 /1970 Van Benthuysen... 338/162 Primary Examiner- -Robert K. Schaefer Assistant ExaminerGerald P. Tolin Attorney-Frederick M. Arbuckle [57] ABSTRACT A miniature potentiometer including a housing having 4 Claims, 5 Drawing Figures g0 80 l 60 I 38- 52 I 56 5g x 26 86 l k MINIATURE POTENTIOMETER WITII STOP RIB AND SEALING MEANS This is a continuation; of application Ser. No. 36,077, filed May I l, 1970 now abandoned.

OBJECTS OFTI-IE INVENTION A broad object of the invention is toprovide a new construction of potentiometer of miniature scale.

Another and more specific object is to'provide aminiature potentiometer that is of unusal accuracy in construction and functioning.

A still more specific'object is toprovide-a miniature I potentiometer of the'character referred to in which the accuracy is produced at least partially by making the accurately interfitting parts.

Another object. is to provide a miniature potentiometer of unusual accuracy of the character just referred to in which the accuracy is achieved at leastspartially by providing certain of the parts with interfitting relationship and thereby positively preventing them from displacement.

A still further object is toprovide a miniature potentiometer in which certain of the parts are press fitted together for accurately relatively positioning them, and retention of them in such proper interfitted relation throughout additionaluse and 'functioning of thepotentiometer.

An additional object is toprovide a miniaturepotentiometer in which certain principal :parts are of molded material, such as plastic,.and which wisprovided with a novel design of conformations including recesses for reception of elements inith electricalcircuit therein.

A further object of theinvention'isto providea miniature potentiometer'of the foregoinggeneral character and'made up. of separateparts, and which are fitted'to gether in a simple manner whereby unusualsavingsin labor are achieved inthe assembly of the parts.

DESCRIPTION or A PREFERRED EMBODIMENT In the drawings:

FIG. 1 is a side viewpartially'in section. andpartially in elevation, showing the miniature potentiometer of the present invention;

FIG. 2 is a top view of the potentiometer;

FIG. 3 is a face view of thexcarrier-assemblytaken at line 3--3 of FIG. 1;

FIG. 4 is a face view of the bottom plate. assembly taken at line 4-4 of FIG. 1; and

FIG. 5 is a sectional viewtaken \at line 5-5 of FIG. 4 and oriented according to FIG. 1.

Referring in detail to the accompanying drawings, the potentiometer of the'inventionis indicated as a whole at 10. As an indication of its'miniature scale, it is noted that it is on the order of one-fourth inchin outer diameter. includes a housing I2, a bottom plate I4, and a carrier 16. The bottom-platemay be molded of plastic while'the housingmaybe of aluminum.

The housing 12 includes a planar top element 18 and a cylindrical side wall 20 concentric with an axis 22, the

the lower open end 28 of the housing member. The rib is shown in cross sectionin FIG. 2. At the lower end of the side wall, and downwardly beyond the rib 26 is a circumferential internal groove 30 and downwardly beyond that groove is a terminal edge element 32 which in the final construction becomes an inclined flange as referred to hereinbelow.

The rotatable carrier 16 is incorporated in a carrier assembly 34 constituting a major component in the-potentiometer. The carrier 16 includes an axial stud or shaft element 36 fitted in the aperture 24 and a body portion 38 'of aradial dimension justshort of the rib 26. Formed-on the body portion is a nose or radial projection 40 which extends radially beyond the rib 26and into proximity to the inner surface of the surrounding wall 20. Upon rotation of the carrier 16 the nose or projection 40 engages the rib 26 on one side or the other at opposite ends of its rotational movement, the ribproviding a limiting stop for such rotation.

1 The carrier 16 is provided with an axial bore 42 for a purpose to be referred to hereinbelow. An O ring gasket 44 of resilient material such as rubber, surrounds the stud 36 and is disposed between the body portion 38-of the carrier and'the top element 18 of the housing.

The stud 36 on its upper or outer endis provided with a screwdriver slot 46 and an indicating arrow 48 cooperative with the indicia25," 27.

Mounted on the-carrier 34' is a contactor or contact spring 50iand for securing this contactor in place (FIG. 3) the carrier is providedtwith a concentric annular rib .52and a boss 54 at the periphery thereof. The contactor includes a body portion 56 having a peripheral notch'58, and includinga collar 60and a resilient arcuate arm 62. The collar 60.is fitted on the rib 52 and the no tch'58 receives the boss 54, both in a press tit, holding the contactor inplace andthe notchboss relation positively presenting the contactor from circumferential displacementrThe arcutate arm 62 preferably at a point "diametrically opposite the notch 58 is provided with a finger 64 for engaging the coil as referred to hereinbelow. For a purpose to be referred to, the collar 60 of thecontactor is at least as great in axial dimension .as the rib 52.

The bottom plate 14 is included in an assembly 66 and includes a main body portion having a circumferentialrib 70 fitted in the groove 30, an upstanding'axial flange 72 preferably and for the most part circumferentially fitted snugly with the surrounding wall thereof. At one side the flange 72 has an axial boss or projection 74 (FIGS.'4,5) having an axial groove 76 therein receivingithe rib 26, and forming alocking arrangement against rotation of the bottomtplate relative to the housing.

The bottom plate includesa central upstanding stud '78having a reduced shank80 at its upper end-titted in the bore 42, and forming bearingmeans for the carrier '16, the conformation forming an'annular shoulder 82.

In the assembly of the device the carrier assembly with the O-ring 44 thereon is first inserted into the housing and then the bottom plate assembly, and the previously straightflange 32 is now peened in around the rib 70 andcemented in place as at 28.

The bottom plate assembly includes a pickup ring 84 having a collar portion 86'fitted over the shank 80 and butted'to theshoulder 82. It has an axial portion 88 fittedxagainstthe boss 78 and preferably in a groove 90 thereon, and a radial foot92 fitted'in a groove 94 (FIG.

4). A terminal contact element 96 has a head 98 electrically secured to the foot 92 and a shank 100 extended through a bore 102 in the bottom plate and cemented in place as indicated at 104 (FIG.

A resistance element 106 in the form of a coil is formed into a circular shape and fitted in the bottom plate, within the flange 72 and cemented in place, the ends of the resistance element terminating adjacent to and on opposite sides of the boss projection 74. At the ends of the coils, are contact elements 108 (FIGS. 4 5) each having a curved element 110 electrically secured to the resistance element and a foot element 112 extending radially inwardly in a groove 114. The bottom plate assembly also includes a pair of terminal contacts 116 each including a head 118 electrically secured to the foot 112, and a shank 120 extending through an aperture 122 and secured in place by cement as at 122.

The resilient O-ring 44 biases the carrier assembly 16 downwardly into engagement with the bottom plate assembly 14 and specifically the collar 60 into firm electrical contact engagement with the collar 86 of the pickup ring 84. The terminal contacts 116 are adapted for connection with suitable conductors for putting the resistance element in circuit while the terminal contact 96 is adapted for incorporation in a circuit for contact engagement through the pickup ring 84 and the contactor 50, and thus the resistance element 106.

The user may apply a screwdriver to the slot 46 and rotate the carrier assembly 16 and thereby move the contactor 50 and finger 64 along the resistance element for the desired setting, and upon the setting of the carrier assembly according to the manual manipulation by the screwdriver, as referred to, the arrow 48 in cooperation with the indica 25 indicates the setting, whilethe terminal indicia elements 27 indicate respectively the minimum and maximum settings.

The shape and proportions of the three main constructional parts namely the housing, the carrier, and the bottom plate, are such that they are well adapted to fabricating techniques, whether molding or otherwise.

The rib 26 on the inner surface of the housing wall, and the cooperation therewith by the groove 76, accurately position the bottom plate assembly, and thus the resistance element 106, and the cross sectional shape of the rib and groove further assures accuracy despite the miniature dimensions encountered. Additionally, the nose or projection 40 in engaging the rib, accurately determines the terminal positions of adjusting movement of the carrier assembly. The contactor 50 and the pickup ring 84 are assured constant and firm contact engagement by the resilience of the O-ring 44. Additionally the resilience of the arcuate arm 62 of the contactor assures constant firm electrical contact engagement with the resistance element. The parts of the device are easily and quickly assembled, with minimum labor required, and consequent economy, and the smaller elements are firmly retained in place, such as the contactor 50 by virtue of its press fit with the central rib 52 and the boss 54 as well as the positive prevention of rotational displacement of the contactor, and further in the rigid securement of the resistance element and the terminal contacts.

We claim:

1. A miniature potentiometer comprising:

a housing including a surrounding wall element having an open end and an opposite end element with a central aperture, the surrounding wallelement having an internal axial rib integrally fon'ned thereon,

a rotatable carrier including a body portion within the housing and an axial stud extending through the aperture, the body portion including a radial projection engageable with the rib thereby limiting rotation of the carrier in each of opposite directions, and a side opposite said stud with an axial bore and a bead in juxtaposition therewith,

resilient means compressed between the end element and the carrier, 7

a bottom plate secured in the housing at the open end thereof and including a central shank extending into the bore of the carrier thereby forming bearing means for the carrier and including a radially exposed groove receiving the rib in the housing and thus positively locking the bottom plate against rotation in the housing, j

a contactor fitted into securement on said bead of the carrier, spaced apart from engagement with the shank and rotatable with the carrier, V

a resistance element mounted on said bottom plate around and spaced apart from said shank and having ends oppositely positioned about said rib,

the contactor having an element self-biased into engagement with the resistance element,

a pick-up ring fixably positioned on the bottom plate in juxtaposition around said shank and'insliding engagement with said contactor, 4

means securing thebottom plate against the housing, and terminal contacts connecting the pick-up ring and the resistance element and exposed to the exterior for connection with conductors.

2. The miniature potentiometer of claim 1 wherein said end element includes a circular series of indicia around the aperture including end limit indications,

said terminal axial rib extends from the end element into proximity with the open end,

said stud extends through said aperture and includes an indicator on the exposed end thereof coopera tive with said indicia on the end element,

said body portion forms an axially disposed shoulder, said resilient means being disposed between said shoulder and the end element of the housing,

said carrier includes a boss at a peripheral position on said side opposite said stud,

said contactor has a planar shape central collar fixably secured on said bead and being of a thickness at least as great as the bead in axial dimension of that bead, the contactor also having a notch receiving said boss and wherein said self-biased element includes an arcuate radially extending finger in engagement with the resistance element, I

said bottom plate includes an axially inwardly directed flange engaging the wall of the housing defining an inner annular space,

said resistance element is positioned in the annular space, said housing has an axis, and said resistance element is shaped into a circle concentric with the housing axis, the resistance element being disposed for operative electrical engagement by the finger of the contactor and the latter sweeping over the resistance element pursuant to rotation of the carrier,

- said resilient means is an O-ring,

said bottom plate includes a central studdirected toward the carrier with said shank extending into the bore, and

said pick-up ring has a planar-shape collar element surrounding the shank and in sliding engagement with the central collar'of the contactor.

3. The miniature potentiometer of claim 2 wherein said housing is internally cup-shaped,

said central stud of the bottom plate includes an axial groove, and i said pick-up ring has an axial element positioned in said groove of said stud and said collar is in abutting sliding and rotational engagement with said said bottom plate.

' II! t k t 

1. A miniature potentiometer comprising: a housing including a surrounding wall element having an open end and an opposite end element with a central aperture, the surrounding wall element having an internal axial rib integrally formed thereon, a rotatable carrier including a body portion within the housing and an axial stud extending through the aperture, the body portion including a radial projection engageable with the rib thereby limiting rotation of the carrier in each of opposite directions, and a side opposite said stud with an axial bore and a bead in juxtaposition therewith, resilient means compressed between the end element and the carrier, a bottom plate secured in the housing at the open end thereof and including a central shank extending into the bore of the carRier thereby forming bearing means for the carrier and including a radially exposed groove receiving the rib in the housing and thus positively locking the bottom plate against rotation in the housing, a contactor fitted into securement on said bead of the carrier, spaced apart from engagement with the shank and rotatable with the carrier, a resistance element mounted on said bottom plate around and spaced apart from said shank and having ends oppositely positioned about said rib, the contactor having an element self-biased into engagement with the resistance element, a pick-up ring fixably positioned on the bottom plate in juxtaposition around said shank and in sliding engagement with said contactor, means securing the bottom plate against the housing, and terminal contacts connecting the pick-up ring and the resistance element and exposed to the exterior for connection with conductors.
 2. The miniature potentiometer of claim 1 wherein said end element includes a circular series of indicia around the aperture including end limit indications, said terminal axial rib extends from the end element into proximity with the open end, said stud extends through said aperture and includes an indicator on the exposed end thereof cooperative with said indicia on the end element, said body portion forms an axially disposed shoulder, said resilient means being disposed between said shoulder and the end element of the housing, said carrier includes a boss at a peripheral position on said side opposite said stud, said contactor has a planar shape central collar fixably secured on said bead and being of a thickness at least as great as the bead in axial dimension of that bead, the contactor also having a notch receiving said boss and wherein said self-biased element includes an arcuate radially extending finger in engagement with the resistance element, said bottom plate includes an axially inwardly directed flange engaging the wall of the housing defining an inner annular space, said resistance element is positioned in the annular space, said housing has an axis, and said resistance element is shaped into a circle concentric with the housing axis, the resistance element being disposed for operative electrical engagement by the finger of the contactor and the latter sweeping over the resistance element pursuant to rotation of the carrier, said resilient means is an O-ring, said bottom plate includes a central stud directed toward the carrier with said shank extending into the bore, and said pick-up ring has a planar-shape collar element surrounding the shank and in sliding engagement with the central collar of the contactor.
 3. The miniature potentiometer of claim 2 wherein said housing is internally cup-shaped, said central stud of the bottom plate includes an axial groove, and said pick-up ring has an axial element positioned in said groove of said stud and said collar is in abutting sliding and rotational engagement with said collar of said contactor.
 4. The miniature potentiometer of claim 3 wherein said notch of said contactor is press-fitted on said boss of said carrier, said bottom plate includes raidal grooves between the central stud and the inwardly directed flange, said pick-up ring has a radial foot element, and said terminal contacts have radial foot elements, said foot elements of said pick-up ring and terminal contacts being positioned in said radial grooves in said bottom plate. 